The present application is directed at pumps in general and more specifically at secondary sealing devices for pumps pumping gases under pressure.
Pumps used in the pumping of L.P.G. (Liquid Petroleum Gases) must meet a safety standard. At present, the failure of a main seal will allow L.P.G. to pass to the outside of the seal flange, vapourize and escape into the atmosphere. As the liquid gas changes state it can reduce the temperature of the leakage point to approxiomately minus 44.degree.F. This causes a build up of ice at that point due to the condensation of the water vapour in the air and this further hampers efforts to stop the leak and make repairs.
During normal operation of the pump, the seal permits a graduated leakage of gas between the seal and the pump shaft and may be tolerated up to a predetermined pressure of, say, 5 psi. Beyond that pressure, a pressure sensing switch starts shut-down of the pump, ultimately resulting in cessation of rotation of the pump shaft. However, the gas continues to leak past the seals and at an increased pressure, thereby presenting the difficult situation described above.